The book explores the ambivalent relationship between identity, agency and personal data in the age of digitalisation. Using qualitative empirical research including a heterogeneous sample the author analyses the conditions under which humans share personal data, construct their selves and act socially.The results show how different data and the meaning attached to them vary over time und thus create distortions and fragmentations in relation to how the self is (re)presented. The subjects face a loss of agency in light of the power ascribed to data, which are often perceived and positioned as objective and unchallengeable. This leads to a sense of unease about sharing data, for which different coping techniques are found. The book critically reflects on these findings and concludes both empirically and theoretically on how identity and agency are constituted in the digital world and the educational implications that result out of this dynamic.